Role of urine immunofixation in the complete response assessment of MM patients other than light-chain-only disease
Juan-José Lahuerta, Ana Jiménez-Ubieto, Bruno Paiva, Joaquín Martínez-López, José González-Medina, Lucía López-Anglada, María-Teresa Cedena, Noemi Puig, Albert Oriol, María-Jesús Blanchard, Rafael Ríos, Jesús Martin, Rafael Martínez, Anna Sureda, Miguel Teodoro Hernández, Javier de la Rubia, Isabel Krsnik, Valentín Cabañas, Luis Palomera, Joan Bargay, María-Victoria Mateos, Laura Rosiñol, Jesús F San Miguel, Joan Blade
Response criteria for multiple myeloma (MM) require monoclonal protein (M-protein)-negative status on both serum immunofixation electrophoresis (sIFE) and urine (uIFE) immunofixation electrophoresis for classification of complete response (CR). However, uIFE is not always performed for sIFE-negative patients. We analyzed M-protein evaluations from 384 MM patients (excluding those with light-chain-only disease) treated in the GEM2012MENOS65 (NCT01916252) trial to determine the uIFE-positive rate in patients who became sIFE-negative posttreatment and evaluate rates of minimal residual disease (MRD)-negative status and progression-free survival (PFS) among patients achieving CR, CR but without uIFE available (uncertain CR; uCR), or very good partial response (VGPR).
Among 107 patients with M-protein exclusively in serum at diagnosis who became sIFE-negative posttreatment and who had uIFE available, the uIFE-positive rate was 0%. Among 161 patients with M-protein in both serum and urine at diagnosis who became sIFE-negative posttreatment, 3 (1.8%) were uIFE positive. Among patients achieving CR vs uCR, there were no significant differences in postconsolidation MRD-negative (<10-6; 76% vs 75%; P = .9) and 2-year PFS (85% vs 88%; P = .4) rates; rates were significantly lower among patients achieving VGPR. Our results suggest that uIFE is not necessary for defining CR in MM patients other than those with light-chain-only disease.